The objectives of this study are to determine the quantitative risks of and qualitative nature of neoplastic disease and diseases with abnormal immunological features in irradiated populations. Three irradiated populations have been under study from 15 to 20 years. This application proposes a continuation of the study. Mail surveys will be carried out to determine the incidence of disease in the subjects and controls. The effectiveness of various survey techniques and accuracy of subject reporting will be evaluated. Patients at high risk of developing neoplastic disease will undergo special studies, e.g., thyroid scans of a subgroup of thymus-irradiated subjects and mammographic and thermographic studies of breast-irradiated women. The effects on the immune system will be evaluated by studies of B and T lymphocytes and tissue antibodies of selected persons.